Continuous-flow machines often have adjustable guide vanes, especially in the front stages of compressors. Depending on the operating state of the continuous-flow machine, they are used to adjust the inflow angles to the runner blades downstream and to regulate the energy conversion of the stage consisting of the guide vanes and the runner blades. When the guide vanes are adjusted, the flow angle changes over the entire height of the channel. When the operating state changes, however, the distribution of the local mass flow along the height of the channel changes. This can diminish the stability of the flow in the continuous-flow machine and reduce the efficiency.
Various measures are known for increasing the stability of the flow in a continuous-flow machine. For example, European patent application EP 0 745 755 A1 describes a specially shaped guide vane for a compressor of a gas turbine. The guide vane has a rear edge that is angled towards the blade root. The use of such guide vanes improves the stability of the flow and thus increases the compressor pump limit. A drawback here is that the geometry of the guide vanes is adapted to a specific operating state and, if a deviation from the operating state occurs, an improved flow is no longer ensured.
German patent application DE 10 2009 023 100 A1 describes a blade device with blades arranged one after the other in the flow direction, whereby the rear edges of the upstream blades are shaped differently from the front edges of the downstream blades, resulting in an irregular distance along the blade edges. This arrangement is also aimed at stabilizing the flow in the continuous-flow machine. This arrangement likewise has the drawback that the geometry of the blades is adapted to a specific operating state.
International patent application WO 2007/042522 A1 describes a blade for a turbo machine in which the chord length along the blade length is irregular. This blade minimizes losses of a blade cascade and is likewise designed for a specific operating range.